Ships, submarines, and other water navigable craft are equipped with highly complex Navigation SONAR Systems (NSS) that interface with the craft's central navigation system through a central navigation computer. These systems employ detailed software and/or firmware and extensive hardware on which such software and/or firmware executes. Such systems measure a ship's velocity. When measuring velocity, SONAR transducers located on the hull of a ship transmit pulses to the ocean bottom. These pulses reflect off the ocean bottom, return to the ship, and are sensed by hydrophones located on the ship's hull. The hydrophones may be in a spatial arrangement, in which there are usually sixteen hydrophones arranged around the perimeter of a square, or in a temporal fashion, one arrangement of which consists of three hydrophones placed at three corners of a square.
When determining velocity, two or more pulses are transmitted to the ocean bottom, reflected off the ocean bottom, received back at the hydrophone array, and correlated amongst the multiple hydrophones to determine which two hydrophones best match the two pulses of interest. The velocity of a ship can then be calculated by dividing the distance between the two correlated hydrophones by twice the time differential between the receipt of the two distinct pulses by the two hydrophones.
Since testing of an NSS at sea is costly and time consuming, a system that simulates the input for an NSS would be very useful to manufacturers and users of SONAR systems, particularly a system which could simulate all ship speeds.